With the huge popularity of coffee and tea in society, there is a demand for greater variety in these beverages. Some of the more common varieties of coffee include, for example, Colombian, French Roast, Kona, and Costa Rican. Some of the more common tea varieties include, for example, Black, Oolong, Green, and White. The preferred water temperature for coffee varies from about 195° F. to about 205° F., whereas the preferred water temperatures for the various types of tea can vary from about 140° F. for high quality green tea to about 208° F. for black tea.
To accommodate these temperature variations, there are several programmable commercial beverage brewing machines available in the market. To operate these units, the programmable features allow a user to select different water temperatures for different types of beverages. Standard commercial brewers typically consist of a large water tank plumbed into the local water system. Because cold water from the tap is under far too much pressure for brewing beverages, the tank is filled and then the connection to the water system is closed. Then the water in the tank is heated to the programmed temperature by means of a large heating coil mounted inside the tank. When the water reaches the correct temperature a valve is opened allowing water to flow out of the tank from a point approximately one sixth of the distance from the top of the tank. The water then flows from the tank to a spray valve, which wets the coffee or tea. This water is gravity fed and is of a low enough pressure to allow for brewing. After approximately one sixth of the tank has been emptied, the valve is closed, the tank is refilled with cold water, and the cycle repeats until the desired amount of beverage has been brewed.
One disadvantage of this type of system is that the large water tank takes a long time to heat. Therefore, it is kept at either the brewing temperature or a slightly lower standby temperature at all times. This wastes a tremendous amount of energy. Another disadvantage is an inability to quickly change water temperature from one beverage temperature to another. On-demand or instant heaters are known for use in beverage systems. Such on-demand or instant heaters are generally defined as heating assemblies that are able to provide an accurate water temperature without requiring a pre-warming time. Typically, a water tank supplies the heater via a water pump controlled by a controller that also controls the heater. However, most beverage brewers with on-demand or instant heaters, and that are plumbed into local water supplies, still require use of a tank of some kind due to the high water pressure in most local water supply lines. In such beverage systems the tank is required to initially receive the higher pressure water from the local water supply line, and where from there it may be gravity fed to the brewing material, at a much lower pressure.
However, because of the complexity involved in these systems, they are often limited to single cup beverage dispensers. Therefore, new approaches are needed for providing variable water temperature in brewing machines that are capable of brewing large, commercial quantities of beverages.